Heating plate with planar heater zones for semiconductor processing

ABSTRACT

An exemplary method is directed to powering heaters in a substrate support assembly on which a semiconductor substrate is supported. The support assembly has an array of heaters powered by two or more power supply lines and two or more power return lines wherein each power supply line is connected to a power supply and at least two of the heaters and each power return line is connected to at least two of the heaters, and a switching device which independently connects each one of the heaters to one of the power supply lines and one of the power return lines so as to provide time-averaged power to each of the heaters by time divisional multiplexing of switches of the switching device. The method includes supplying power to each of the heaters sequentially using a time-domain multiplexing scheme.

BACKGROUND OF THE DISCLOSURE

With each successive semiconductor technology generation, substratediameters tend to increase and transistor sizes decrease, resulting inthe need for an ever higher degree of accuracy and repeatability insubstrate processing. Semiconductor substrate materials, such as siliconsubstrates, are processed by techniques which include the use of vacuumchambers. These techniques include non plasma applications such aselectron beam deposition, as well as plasma applications, such assputter deposition, plasma-enhanced chemical vapor deposition (PECVD),resist strip, and plasma etch.

Plasma processing systems available today are among those semiconductorfabrication tools which are subject to an increasing need for improvedaccuracy and repeatability. One metric for plasma processing systems isincreased uniformity, which includes uniformity of process results on asemiconductor substrate surface as well as uniformity of process resultsof a succession of substrates processed with nominally the same inputparameters. Continuous improvement of on-substrate uniformity isdesirable. Among other things, this calls for plasma chambers withimproved uniformity, consistency and self diagnostics.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a heating plate for a substratesupport assembly used to support a semiconductor substrate in asemiconductor plasma processing apparatus, comprises at least a firstelectrically insulating layer, planar heater zones comprising at leastfirst, second, third and fourth planar heater zones laterallydistributed across the first electrically insulating layer, electricallyconductive power supply lines comprising at least a first power supplyline electrically connected to the first and second heater zones and asecond power supply line electrically connected to the third and fourthheater zones, electrically conductive power return lines comprising atleast a first power return line electrically connected to the first andthird heater zones, and a second power return line electricallyconnected to the second and fourth heater zones.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of the cross-sectional view of a substrate supportassembly in which a heating plate with an array of heater zones isincorporated, the substrate support assembly also comprising anelectrostatic chuck (ESC).

FIG. 2 illustrates the topological connection between power supply andpower return lines to an array of heater zones in one embodiment of aheating plate which can be incorporated in a substrate support assembly.

FIG. 3A shows an embodiment wherein the power supply lines and theheater zones are on the same plane.

FIG. 3B shows the power return lines on a plane separated from the planein FIG. 3A by an electrically insulating layer and the power returnlines are connected to the heater zones through vias extending throughthe electrically insulating layer.

FIG. 3C is a schematic of the cross-sectional view of a substratesupport assembly in which the heating plate of FIG. 3A and 3B isincorporated.

FIG. 4A shows an embodiment wherein the power supply lines and theheater zones are on the same plane.

FIG. 4B shows a plane separated from the plane in FIG. 4A by anelectrically insulating layer wherein the power supply lines areconnected to leads in this plane through vias, and brought to a singlehole in the cooling plate (not shown). The power return lines on thisplane are connected to the heater zones through vias extending betweenthis plane and the plane in FIG. 4A. The power return lines are alsobrought to a single hole in the cooling plate (not shown).

FIG. 5A shows an embodiment wherein the heater zones are on a planewithout the power supply lines or power return lines on that plane. Theheater zones are connected to power supply lines and power return lineson one or more different planes through vias.

FIG. 5B shows the power supply lines on a second plane separated fromthe plane in FIG. 5A by an electrically insulating layer. The powersupply lines are connected to the heater zones through vias extendingbetween the two planes in FIG. 5A and 5B.

FIG. 5C shows the power return lines on a third plane separated from theplanes in FIG. 5A and 5B by another electrically insulating layer. Thepower return lines are connected to the heater zones through viasextending between all three planes in FIG. 5A-C. The leads connected tothe power supply lines in FIG. 5B are also routed through feedthroughsin this plane.

FIG. 5D is a schematic of the cross-sectional view of a substratesupport assembly in which the heating plate in FIG. 5A-C isincorporated.

FIG. 5E is a schematic of the cross-sectional view of a substratesupport assembly in which an alternative heating plate in FIG. 5A-C isincorporated.

FIG. 6 is a schematic of the cross-sectional view of a substrate supportassembly in which a heating plate is incorporated, the substrate supportassembly further including a primary heater layer above the array ofheater zones, the primary heater located on an additional planeseparated from all the planes in the heating plate by an electricallyinsulating layer.

FIG. 7A is a schematic of an exemplary plasma processing chamber, whichcan include a substrate support assembly with the heating platedescribed herein.

FIG. 7B is a schematic of an RF isolation approach.

FIG. 8 shows a block diagram of signal flow in one embodiment of thecontrol electronics for the substrate support assembly.

DETAILED DESCRIPTION

Radial and azimuthal substrate temperature control in a semiconductorprocessing apparatus to achieve desired critical dimension (CD)uniformity on the substrate is becoming more demanding. Even a smallvariation of temperature may affect CD to an unacceptable degree,especially as CD approaches sub-100 nm in semiconductor fabricationprocesses.

A substrate support assembly may be configured for a variety offunctions during processing, such as supporting the substrate, tuningthe substrate temperature, and power supplying radio frequency power.The substrate support assembly can comprise an electrostatic chuck (ESC)useful for electrostatically clamping a substrate onto the substratesupport assembly during processing. The ESC may be a tunable ESC(T-ESC). A T-ESC is described in commonly assigned U.S. Pat. Nos.6,847,014 and 6,921,724, which are hereby incorporated by reference. Thesubstrate support assembly may comprise a ceramic substrate holder, afluid-cooled heat sink (hereafter referred to as cooling plate) and aplurality of concentric heater zones to realize step by step and radialtemperature control. Typically, the cooling plate is maintained between0° C. and 30° C. The heaters are located on the cooling plate with alayer of thermal insulator in between. The heaters can maintain thesupport surface of the substrate support assembly at temperatures about0° C. to 80° C. above the cooling plate temperature. By changing theheater power within the plurality of heater zones, the substrate supporttemperature profile can be changed between center hot, center cold, anduniform. Further, the mean substrate support temperature can be changedstep by step within the operating range of 0 to 80° C. above the coolingplate temperature. A small azimuthal temperature variation posesincreasingly greater challenges as CD decreases with the advance ofsemiconductor technology.

Controlling temperature is not an easy task for several reasons. First,many factors can affect heat transfer, such as the locations of heatsources and heat sinks, the movement, materials and shapes of the media.Second, heat transfer is a dynamic process. Unless the system inquestion is in heat equilibrium, heat transfer will occur and thetemperature profile and heat transfer will change with time. Third,non-equilibrium phenomena, such as plasma, which of course is alwayspresent in plasma processing, make theoretical prediction of the heattransfer behavior of any practical plasma processing apparatus verydifficult if not impossible.

The substrate temperature profile in a plasma processing apparatus isaffected by many factors, such as the plasma density profile, the RFpower profile and the detailed structure of the various heating thecooling elements in the chuck, hence the substrate temperature profileis often not uniform and difficult to control with a small number ofheating or cooling elements. This deficiency translates tonon-uniformity in the processing rate across the whole substrate andnon-uniformity in the critical dimension of the device dies on thesubstrate.

In light of the complex nature of temperature control, it would beadvantageous to incorporate multiple independently controllable heaterzones in the substrate support assembly to enable the apparatus toactively create and maintain the desired spatial and temporaltemperature profile, and to compensate for other adverse factors thataffect CD uniformity.

Described herein is a heating plate for a substrate support assembly ina semiconductor processing apparatus with multiple independentlycontrollable heater zones. This heating plate comprises a scalablemultiplexing layout scheme of the heater zones and the power supply andpower return lines. By tuning the power of the heater zones, thetemperature profile during processing can be shaped both radially andazimuthally. Although this heating plate is primarily described for aplasma processing apparatus, this heating plate can also be used inother semiconductor processing apparatuses that do not use plasma.

Also described are methods for manufacturing this heating plate, asubstrate support assembly comprising such a heating plate, and methodsfor powering and controlling a substrate support assembly comprisingsuch a heating plate.

The heater zones in this heating plate are preferably arranged in adefined pattern, for example, a rectangular grid, a hexagonal grid, apolar array, concentric rings or any desired pattern. Each heater zonemay be of any suitable size and may have one or more heater elements.All heater elements in a heater zone are turned on or off together. Tominimize the number of electrical connections, power supply and powerreturn lines are arranged such that each power supply line is connectedto a different group of heater zones and each power return line isconnected to a different group of heater zones with each heater zonebeing in one of the groups connected to a particular power supply lineand one of the groups connected to a particular power return line. Notwo heater zones are connected to the same pair of power supply andpower return lines. Thus, a heater zone can be activated by directingelectrical current through a pair of power supply and power return linesto which this particular heater zone is connected. The power of theheater elements is preferably smaller than 20 W, more preferably 5 to 10W. The heater elements may be resistive heaters, such as polyimideheaters, silicone rubber heaters, mica heaters, metal heaters (e.g. W,Ni/Cr alloy, Mo or Ta), ceramic heaters (e.g. WC), semiconductor heatersor carbon heaters. The heater elements may be screen printed, wire woundor etched foil heaters. In one embodiment, each heater zone is notlarger than four device dies being manufactured on a semiconductorsubstrate, or not larger than two device dies being manufactured on asemiconductor substrate, or not larger than one device die beingmanufactured on a semiconductor substrate, or between 2 and 3 cm² inarea to correspond to the device dies on the substrate. The thickness ofthe heater elements may range from 2 micrometers to 1 millimeter,preferably 5-80 micrometers. To allow space between heater zones and/orpower supply and power return lines, the total area of the heater zonesmay be up to 90% of the area of the upper surface of the substratesupport assembly, e.g. 50-90% of the area. The power supply lines or thepower return lines (power lines, collectively) may be arranged in gapsranging from 1 to 10 mm between the heater zones, or in separate planesseparated from the heater zones plane by electrically insulating layers.The power supply lines and the power return lines are preferably made aswide as the space allows, in order to carry large current and reduceJoule heating. In one embodiment, in which the power lines are in thesame plane as the heater zones, the width of the power lines ispreferably between 0.3 mm and 2 mm. In another embodiment, in which thepower lines are on different planes than the heater zones, the width ofthe power lines can be as large as the heater zones, e.g. for a 300 mmchuck, the width can be 1 to 2 inches. The materials of the power supplyand power return lines may be the same as or different from thematerials of the heater elements. Preferably, the materials of the powersupply and power return lines are materials with low resistivity, suchas Cu, Al, W, Inconel® or Mo.

FIGS. 1-2 show a substrate support assembly comprising one embodiment ofthe heating plate having an array of heater zones 101 incorporated intwo electrically insulating layers 104A and 104B. The electricallyinsulating layers may be a polymer material, an inorganic material, aceramic such as silicon oxide, alumina, yttria, aluminum nitride orother suitable material. The substrate support assembly furthercomprises (a) an ESC having a ceramic layer 103 (electrostatic clampinglayer) in which an electrode 102 (e.g. monopolar or bipolar) is embeddedto electrostatically clamp a substrate to the surface of the ceramiclayer 103 with a DC voltage, (b) a thermal barrier layer 107, (c) acooling plate 105 containing channels 106 for coolant flow.

As shown in FIG. 2, each of the heater zones 101 is connected to one ofthe power supply lines 201 and one of the power return lines 202. No twoheater zones 101 share the same pair of power supply 201 and powerreturn 202 lines. By suitable electrical switching arrangements, it ispossible to connect a pair of power supply 201 and power return 202lines to a power supply (not shown), whereby only the heater zoneconnected to this pair of lines is turned on. The time-averaged heatingpower of each heater zone can be individually tuned by time-domainmultiplexing. In order to prevent crosstalk between different heaterzones, a rectifier 250 (e.g. a diode) may be serially connected betweeneach heater zone and the power supply lines connected thereto (as shownin FIG. 2), or between each heater zone and the power return linesconnected thereto (not shown). The rectifier can be physically locatedin the heating plate or any suitable location. Alternatively, anycurrent blocking arrangement such as solid state switches can be used toprevent crosstalk.

FIGS. 3A, 3B and 3C show a substrate support assembly comprising an ESC,a cooling plate, and one embodiment of the heating plate wherein theheater zones 101 and power supply lines 201 are arranged in a firstplane 302, and the power return lines 202 are arranged in a second plane303 separated from the first plane 302 by an electrically insulatinglayer 304. The power return lines 202 are connected to the heater zones101 by conductive vias 301 in the electrically insulating layer 304,extending between the first plane 302 and the second plane 303.

In use, the power supply lines 201 and power return lines 202 areconnected to circuitry external to the heating plate through holes orconduits in the cooling plate. It should be appreciated that thepresence of holes or conduits in the cooling plate can affect thetemperature uniformity of substrate support assembly adversely,therefore reducing the number of holes or conduits in the cooling platecan enhance temperature uniformity. In addition, a small number of holesmakes placing them around the edge of the substrate support assemblypossible. For example, a single power supply conduit in the coolingplate can be used to feed electrical leads to the power supply lines201. In one embodiment (FIG. 4A and 4B), the heater zones 101 and powersupply lines 201 are arranged in a first plane 402. The power supplylines 201 are connected to leads 404 in a second plane 403 throughconductive vias 301 extending between the first plane 402 and the secondplane 403. The second plane 403 is separated from the first plane 402 byan electrically insulating layer (not shown). The power return lines 202are arranged in the second plane 403 and are connected to the heaterzones 101 through conductive vias 301 extending between the first plane402 and the second plane 403. In the second plane 403, the leads 404 arebrought through a hole or conduit 401 in the cooling plate whilemaintaining electrical insulation between the leads. Similarly, thepower return lines 202 are connected to leads 405 brought through a holeor conduit 406 in the cooling plate while maintaining electricalinsulation between the leads 405.

FIGS. 5A, 5B, 5C and 5D show a substrate support assembly comprising yetanother embodiment of the heating plate, the heater zones 101 arearranged in a first plane 501; the power supply lines 201 are arrangedin a second plane 502; and the power return lines 202 are arranged in athird plane 503. The first plane 501, second plane 502 and third plane503 are separated from each other by electrically insulating layers 504and 304. The power supply lines 201 and power return lines 202 areconnected to the heater zones 101 through conductive vias 301 in theelectrically insulating layers 304 and 504, extending between the planes501, 502 and 503. Leads (not shown) connected to the power supply lines201 are routed through holes or conduits 505 in the layer 504. It shouldbe appreciated that the planes 501, 502 and 503 may be arranged in anyorder in the vertical direction, provided that the vias and conduits aresuitably arranged. Preferably, the heaters are arranged closest to thesubstrate support assembly upper surface. FIG. 5E shows an embodimentwherein each heater zone 101 is connected to the power return line 202through a rectifier 506 (e.g. a diode). The rectifier 506 only allowselectric current flowing from the power supply line 201 through theheater zone 101 to the power return line 202, and thus preventscrosstalk between heater zones.

The substrate support assembly can comprise an additional electricallyinsulating layer 604 in which one or more additional heaters (hereafterreferred to as primary heaters 601) are incorporated (FIG. 6).Preferably, the primary heaters 601 are individually controlledhigh-power heaters. The power of the primary heaters is between 100 and10000W, preferably, between 1000 and 5000W. The primary heaters may bearranged as a rectangular grid, concentric annular zones, radial zone orcombination of annular zones and radial zones. The primary heaters maybe used for changing the mean temperature, tuning the radial temperatureprofile, or step-by-step temperature control on the substrate. Theprimary heaters may be located above or below the heater zones of theheating plate.

In one embodiment, at least one of the insulating layers in the heatingplate is a sheet of polymer material.

In another embodiment, at least one of the insulating layers in theheating plate is a sheet of inorganic material such as ceramic orsilicon oxide. Examples of suitable insulating and conductive materialfor use in manufacture of ceramic chucks are disclosed in commonlyassigned U.S. Pat. No. 6,483,690, the disclosure of which is herebyincorporated by reference.

A substrate support assembly can comprise an embodiment of the heatingplate, wherein each heater zone of the heating plate is of similar sizeto or smaller than a single device die or group of device dies on thesubstrate so that the substrate temperature, and consequently the plasmaetching process, can be controlled for each device die position tomaximize the yield of devices from the substrate. The scalablearchitecture of the heating plate can readily accommodate the number ofheater zones required for die-by-die substrate temperature control(typically more than 100 dies on a substrate of 300-mm diameter) withminimal number of power supply lines, power return lines, andfeedthroughs in the cooling plate, thus reduces disturbance to thesubstrate temperature, the cost of manufacturing and complexity of thesubstrate support assembly. Although not shown, the substrate supportassembly can comprise features such as lift pins for lifting thesubstrate, helium back cooling, temperature sensors for providingtemperature feedback signals, voltage and current sensors for providingheating power feedback signals, power feed for heaters and/or clampelectrode, and/or RF filters.

In one embodiment of the method for manufacturing the heating plate,where the insulating layers are ceramic, the insulating layers may beformed by depositing the ceramic on a suitable substrate usingtechniques such as plasma spraying, chemical vapor deposition orsputtering. This layer can be an initial starting layer or one of theinsulating layers of the heating plate.

In one embodiment of the method for manufacturing the heating plate,where the insulating layers are ceramic, the insulating layers may beformed by pressing a mixture of ceramic powder, binder and liquid intosheets and drying the sheets (hereafter referred as green sheets). Thegreen sheets can be about 0.3 mm in thickness. The vias may be formed inthe green sheets by punching holes in the green sheets. The holes arefilled with a slurry of conducting powder. The heater elements, powersupply and power return lines may be formed by: screen printing a slurryof conducting powder (e.g. W, WC, doped SiC or MoSi₂), pressing a precutmetal foil, spraying a slurry of conducting powder, or any othersuitable technique. Recesses for accommodating any rectifiers such asdiodes may be pressed during the forming process of the green sheets orcut in the green sheets after the forming process. Discrete componentrectifiers may be mounted into these recesses. Multiple green sheetswith a variety of components (power lines, vias, rectifiers and heaterelements) are then aligned, pressed and sintered to form an entireheating plate.

In another embodiment of the method for manufacturing the heating plate,where the insulating layers are ceramic, the insulating layers may beformed by pressing a mixture of ceramic powder, binder and liquid intogreen sheets and drying the green sheets. The green sheets can be about0.3 mm in thickness. Holes are punched in the green sheets foraccommodating vias. Recesses for accommodating any rectifiers such asdiodes may be pressed during the forming process of the green sheets orcut in the green sheets after the forming process. Then, individualgreen sheets are sintered. The holes in the sintered sheets foraccommodating vias are filled with a slurry of conducting power. Theheater elements, power supply and power return lines may be screenprinted with a slurry of conducting powder (e.g. W, WC, doped SiC orMoSi₂), or be formed using any other suitable technique, on the sinteredsheets. Discrete component rectifiers may be mounted into the recessesin the sintered sheets. Multiple sintered sheets with a variety ofcomponents (lines, vias, rectifiers and heater elements) are thenaligned and bonded with an adhesive to form an entire heating plate.

In one embodiment where the insulating layers are silicon oxide sheets,the insulating layers may be formed by depositing a thin film siliconoxide onto a suitable substrate using techniques such as evaporation,sputtering, PVD, CVD, PECVD.

In one preferred embodiment of the method for manufacturing the heatingplate, a thin metal sheet (component layer) such as Al, Inconel® or Cufoil, is bonded (e.g. heat pressed, adhered with adhesive) to a firstpolymer film such as polyimide. A patterned resist film is applied tothe surface of the component layer wherein the patterns define theshapes and positions of the electrical components such as heaterelements, power supply lines or power return lines. The exposed metal ischemically etched and the resist pattern is retained in the remainingmetal sheet. The resist is then removed by dissolution in a suitablesolvent or dry stripping. A second polymer film with holes foraccommodating vias (via layer) is aligned and bonded to the firstpolymer film. The sidewalls of the holes may be coated by plating metaltherein. Any suitable number of component layers and via layers may beincorporated serially. Finally, exposed metal components are covered bya continuous polymer film for electrical insulation.

In another embodiment, the heater elements, power supply and powerreturn lines are made of metal films deposited (e.g. plasma sprayed,electroplated, chemical vapor deposition, or sputtered) on an insulatinglayer or substrate (e.g. a green sheet).

In another embodiment, the heater elements, power supply and powerreturn lines are made of a thin layer of amorphous conductive inorganicfilm such as indium tin oxide deposited (e.g. electroplated, chemicalvapor deposition, or sputtered) on an insulating layer or substrate(e.g. a green sheet).

In yet another embodiment, the heater elements, power supply and powerreturn lines are made of a thin layer of conductive ceramic filmdeposited (e.g. chemical vapor deposition, or sputtered) on aninsulating layer or substrate (e.g. a green sheet).

In one embodiment, the power supply and power return lines in theheating plate may be connected to the external circuitry by terminalconnectors such as spring tipped passthroughs embedded in butelectrically insulated from the cooling plate.

In another embodiment, the power supply and power return lines in theheating plate may be connected to the external circuitry by attaching(soldered, bonded with conductive adhesive or spot welded) lead wires tothe power supply and power return lines and threading these lead wiresthrough holes or conduits in the cooling plate.

In a plasma processing system, the RF power applied in the plasmaprocessing chamber is usually above 100W, sometimes above 1000W. Theamplitude of RF voltages can exceed a kilovolt. Such strong RF power caneasily affect the operation of the control and power circuit of theheater zones without proper filtration or isolation. An RF filter can beused to shunt the RF power away from the control and power circuit. AnRF filter may be a simple broad-band filter or a tuned-filter for thespecific RF frequencies used in the plasma processing system. An RFisolator, in contrast, eliminates direct electrical connection betweenany RF-coupled components and the control and power circuit. An RFisolator may be an optical coupler or a transformer.

As an overview of how a plasma processing chamber operates, FIG. 7Ashows a schematic of a plasma processing chamber comprising a chamber713 in which an upper showerhead electrode 703 and a substrate supportassembly 704 are disposed. A substrate 712 is loaded through a loadingport 711 onto the substrate support assembly 704. A gas line 709supplies process gas to the upper showerhead electrode 703 whichdelivers the process gas into the chamber. A gas source 708 (e.g. a massflow controller power supplying a suitable gas mixture) is connected tothe gas line 709. A RF power source 702 is connected to the uppershowerhead electrode 703. In operation, the chamber is evacuated by avacuum pump 710 and the RF power is capacitively coupled between theupper showerhead electrode 703 and a lower electrode in the substratesupport assembly 704 to energize the process gas into a plasma in thespace between the substrate 712 and the upper showerhead electrode 703.The plasma can be used to etch device die features into layers on thesubstrate 712. The substrate support assembly 704 may have heatersincorporated therein. It should be appreciated that while the detaileddesign of the plasma processing chamber may vary, RF power is coupledthrough the substrate support assembly 704.

FIG. 7B shows a schematic of an embodiment of RF filtration orisolation, wherein no filters or isolators are connected on the heaterzone power supply and power return lines and the control and powercircuit 705 is connected to a filter or isolator 706B, which isconnected to the electric ground 701. The primary heaters (not shown),if present in the substrate support assembly, preferably have separatefilters or isolators due to their high power. In this approach, thecontrol and power circuit 705 floats at the RF potential or “high side”.This approach allows multiple heater zones to share only one filter orisolator.

All the high side circuitry can be housed inside a local floatingFaraday cage immediately under the substrate support assembly basestructure.

Alternatively, an isolation transformer is used as the single filter orisolator 706B to isolate the power and control circuitry 705 from theRF. The control and power circuitry 705 of the heater zones should becapable of operating at relatively high frequency (25 to 250 KHz)because the transformer strongly attenuates DC and low frequencytransmission. The control and power circuitry is referenced to a singlefloating potential (floating ground). This requires that the control andpower circuitry connected to this isolation transformer must be subjectto very similar RF exposure. If the RF potentials differ substantiallybetween two groups of control and power circuits, significant RF currentflows between these groups. In this scenario, each group must have itsown filter or isolator, or there must be a filter or isolator betweenthese groups.

The filter or isolator 706B may be physically located in the plasmaprocessing chamber or any other suitable location.

One embodiment of the heater control electronics is depicted in FIG. 8.A low side controller 809 may be a microcontroller unit (MCU) or ahigher level device such as a computer (PC). Through an optical coupler807, the low side controller communicates digitally to the high side MCU805 which interacts with the heater zones 801, sensors 803, and anyauxiliary circuits 802. If the high side MCU 805 has sufficientcapability and local memory, any set-point and program may be preloadedinto the high side MCU 805 before each run, thus eliminating the need ofa real-time link to the low side controller 809. 804 represents one-waycommunication links between modules. 806 represents two-waycommunication links between modules.

In one embodiment of time-domain multiplexing schemes, the high side MCUsupplies power to each heater zone power supply line sequentially. Onlyone power supply line is connected to a power supply at the same time.During the time when one power supply line is powered, the high side MCUmay keep any or all power return lines connected to the floatingreference for a portion of this duration. A heater zone is turned onwhen at least one of the power supply lines connected to this heaterzone is connected to the power supply, and at least one of the powerreturn lines connected to this heater zone is connected to the floatingreference. The average power of a heater zone is directly proportionalto the average duration it is turned on. Alternatively, during the timewhen one power supply line is powered, the high side MCU may keep any orall power return lines connected to the floating reference for thisentire duration and regulate the power transmitted to each heater zonethat is turned on.

For example, with a 10-by-10 grid of heater zones, heater zones in rownumber N are connected to a power supply line number N; heater zones incolumn number M are connected to a power return line number M. The highside MCU may control heating such that each of the power supply lines isconnected to the power supply for 100 ms, sequentially. For example,during the 100 ms of time when power supply line number 3 is connectedto the power supply, the MCU is operable to connect power return linesnumber 7, 8, and 9 to the floating reference for 10, 50 and 100 ms,respectively, as directed by the particular heating requirement duringthis 100 ms. Thus, the heater zone in row number 3 and column number 7has a duty cycle of 1%; the heater zone in row number 3 and columnnumber 8 has a duty cycle of 5%; the heater zone in row number 3 andcolumn number 9 has a duty cycle of 10%. In this particular example, themaximum peak power for each heater zone would be set to ten times theaverage maximum power desired.

In order to prevent detectable temperature modulation, the switchingfrequencies and the entire multiplexing scheme are preferablysufficiently rapid that each heater zone gets addressed frequently (atleast 1 Hz). Additional loop control may be implemented using feedbackdata from one of more temperature sensors. Voltage and current sensorscan also be implemented if desired. These sensors can be configured tomeasure parameters such as temperatures on different locations on thesubstrate and power of heater zones. These measured parameters are sentto the control and power circuit to be compared with set targets ofthese parameters so that the control and power circuit can adjust thepower delivered to the heater zones accordingly in order to minimize thedifference between the measured parameters and their set targets.

While a heating plate, methods of manufacturing the heating plate, asubstrate support assembly comprising the heating plate, and a method ofusing a plasma processing chamber containing the substrate supportassembly have been described in detail with reference to specificembodiments thereof, it will be apparent to those skilled in the artthat various changes and modifications can be made, and equivalentsemployed, without departing from the scope of the appended claims. Forinstance, the substrate support assembly can include temperature sensorsfor monitoring substrate temperature, a power feed arrangement to powerthe ESC with desired clamping voltage, a lifting pin arrangement forraising and lowering a substrate, a heat transfer gas feed arrangementfor supplying gas such as helium to the underside of the substrate, atemperature controlled liquid feed arrangement to supply heat transferliquid to the cooling plate, a power feed arrangement to individuallypower primary heaters above or below the planar heater zones, a powerfeed arrangement to supply RF power at one or more frequencies to alower electrode incorporated in the substrate support assembly, and thelike.

1.-22. (canceled)
 23. A method of powering heaters in a substratesupport assembly on which a semiconductor substrate is supported, thesupport assembly having an array of heaters powered by two or more powersupply lines and two or more power return lines wherein each powersupply line is connected to a power supply and at least two of theheaters and each power return line is connected to at least two of theheaters, and a switching device which independently connects each one ofthe heaters to one of the power supply lines and one of the power returnlines so as to provide time-averaged power to each of the heaters bytime divisional multiplexing of switches of the switching device, themethod comprising: supplying power to each of the heaters sequentiallyusing a time-domain multiplexing scheme.
 24. The method of claim 23,wherein only one power supply line is connected to a power supply at thesame time.
 25. The method of claim 23, wherein an average power of eachof the heaters is directly proportional to an average duration of timethat heater is turned on.
 26. The method of claim 23, wherein the arrayof heaters are arranged in a grid, the method further comprising:connecting heaters in row number N with a power supply line number N;and connecting heaters in column M connected to a power return linenumber M.
 27. The method of claim 23, further comprising: sequentiallyconnecting each of the power supply lines to a power supply.
 28. Themethod of claim 23, further comprising: addressing each heater at afrequency of at least 1 Hz.
 29. The method of claim 23, wherein:measuring, via sensors, parameters of the substrate and the heaters;sending the measured parameters to a control and power circuit; andadjusting power delivered to the heaters to minimize differences betweenthe measured parameters and set targets.
 30. The method of claim 23,wherein the substrate support includes a control and power circuit, themethod further comprising: sequentially supply power, via the controland power circuit, to at least 16 heaters.
 31. The method of claim 23,wherein at least one primary heater layer is arranged above or below afirst electrically insulating layer of a heating plate supporting theheaters, wherein the primary heater layer is electrically insulated fromthe heaters, the power supply lines, and the power return lines; theprimary heater layer includes at least one heater which provides meantemperature control of the semiconductor substrate; the heaters provideradial and azimuthal temperature profile control of the semiconductorsubstrate, the method comprising: powering the primary planar heaterlayer to a predetermined temperature; and plasma processing thesemiconductor substrate at the predetermined temperature.
 32. The methodof claim 23, further comprising: (a) loading a semiconductor substrateinto the processing chamber and positioning the semiconductor substrateon the substrate support assembly; (b) determining a temperature profilethat compensates for processing conditions affecting critical dimension(CD) uniformity; (c) heating the semiconductor substrate to conform tothe temperature profile using the substrate support assembly; (d)igniting plasma and processing the semiconductor substrate whilecontrolling the temperature profile by independently controlled heatingof the heaters; and (e) unloading the semiconductor substrate from theprocessing chamber and repeating steps (a)-(e) with a differentsemiconductor substrate.
 33. The method of claim 32, wherein theprocessing comprises plasma etching the semiconductor substrate.
 34. Themethod of claim 23, further comprising: supplying one power supply linewith power; and during the supply of power to the one power supply line:selecting return lines to be activated; and connecting a plurality ofthe selected return lines to a floating reference for identical ordifferent time durations to regulate power supplied to heaters connectedto the power supply line and the selected return lines.
 35. The methodof claim 23, wherein the heaters are sized such that: (a) each heater isnot larger than four device dies being manufactured on the semiconductorsubstrate, or (b) each heater is not larger than two device dies beingmanufactured on the semiconductor substrate, or (c) each heater is notlarger than one device die being manufactured on the semiconductorsubstrate, or (d) the area of each heater is between 2 and 3 squarecentimeters, or (e) the heater array includes 100 to 400 planar heaters,or (f) each heater heats a planar heater zone of 1 to 15 cm², or (g)each heater heats a planar heater zone of 16 to 100 cm², or (h) eachheater is scaled with sizes of device dies on the semiconductorsubstrate and the overall size of the semiconductor substrate.
 36. Themethod of claim 23, wherein the total number of the power supply linesand the power return lines is equal to or less than the total number ofthe heaters.
 37. The method of claim 23, wherein the heaters arearranged in a rectangular grid, hexagonal grid or concentric rings; andthe heaters are separated from each other by gaps at least 1 millimeterin width and at most 10 millimeters in width.
 38. The method of claim23, wherein a rectifier is serially connected between each heater andthe power supply line connected thereto, or a rectifier is seriallyconnected between each heater and the power return line connectedthereto.
 39. The method of claim 23, wherein the heaters are resistiveheaters and the maximum power supplied to the resistive heaters is 20 W.40. The method of claim 23, further comprising: individually tuning atime averaged heating power of each heater by the time-domainmultiplexing.
 41. The method of claim 23, wherein the substrate supportassembly includes primary heaters powered with 100 to 10,000 W, theprimary heaters located below the array of heaters.